1. Field of the Invention
The present invention relates to a dual component oral care composition which is stable and efficacious in effecting heightened whitening of teeth.
2. The Prior Art
Many substances such as tea and coffee that a person confronts or comes in contact with on a daily basis can "stain" or reduce the "whiteness" of one's teeth. Consumers consider clean, white teeth to be aesthetically desirable. Dull-looking, stained teeth are objectionable to most people both on the basis of cosmetic appearance and also socially as an indication of poor oral hygiene.
Dental gels containing active oxygen liberating ingredients such as hydrogen peroxide, urea peroxide, percarbonates and perborates of alkali and alkaline earth metals have been disclosed in the prior art for whitening teeth. For example, U.S. Pat. No. 5,766,574 discloses a dual component dental whitening composition which comprises packaging a first gel component containing a peroxide compound and a second paste component containing silica present in amounts which is incompatible with the peroxide, the first and second dentifrice components being maintained separate from the other in a dual chambered container or tube until dispensed and combined for application to teeth requiring whitening.
It has been further determined that many dentifrice thickening or gelling agents are incompatible with hydrogen peroxide. Organic thickeners such as polyoxyethylene oxide/polypropylene oxide block copolymers although compatible with hydrogen peroxide, the block copolymer structure completely collapses when the dentifrice component containing the polymer comes in contact even for a short time, as in U.S. Pat. No. 5,766,574 with a dentifrice containing an incompatible ingredient, whereby the gel is converted to an unacceptable liquid state. This phenomenon is especially troublesome when small amounts of paste and gel residue mix at the tip of the dual chambered dentifrice dispenser, which results in a liquid forming that dribbles down the dispenser surface which is unappealing to the consumer. When the two components are packaged in a dual chambered tube wherein there is a pinhole, or tear in the dividing membrane, liquefaction of the gel occurs, especially during storage at elevated temperatures, e.g., 120.degree. F.
Although the composition disclosed in U.S. Pat. No. 5,766,574 is effective for whitening, when a noncationic antiplaque agent such as Triclosan is included in the abrasive dentifrice component, it was discovered that when the peroxide gel and paste components were combined for application to the teeth, the bioavailability of the Triclosan was inhibited to a level whereby a limited antiplaque benefit was achieved. Investigation of this problem led to the discovery that polyethylene oxide/polypropylene oxide block copolymers conventionally used as a thickening agents in the preparation of peroxide gels were the factor responsible for the impairment of the antiplaque efficacy of the Triclosan. A solution to this problem is disclosed in copending application U.S. Ser. No. 09/166,025 which is directed to a dental product capable of delivering both an antiplaque agent such as Triclosan and a peroxide whitening agent whereby the ingredients used to prepare the dentifrice composition do not inhibit the bioavailability of the antiplaque agent so that optimum antiplaque and whitening benefits result, wherein the antibacterial agent and/or peroxide compound are each incorporated in separate dentifrice components which are physically separated until dispensed for use, the first component being an aqueous composition containing the nonionic antibacterial agent and the second component containing a peroxide whitening compound in a vehicle thickened with a combination of a inorganic thickener and an organic thickener other than an alkylene oxide polymer, whereby unimpaired antiplaque, and whitening benefits are achieved upon mixing of the components on application to the teeth.
It has now been determined that the combination of thickener ingredients used in the peroxide gels of U.S. Ser. No. 09/166,025 also impart storage stability to the gel so that the gel does not liquefy when in contact with the paste component.